The present objectives of this research program are to test a model of convulsive activity, to measure extracellular and transmembrane currents during such activity, and also to analyze the r wave produced by medullary pyramid stimulation. The model proposes that antidromic activity is induced in layer I thalamocortical fibers and that this activity induces, via deep layer III collaterals, calcium spikes on layer III and II interneurons. Various membrane stabilizing agents (e.g., taurine) will be tested to block the antidromic action. Ba ions and Mn ions will be tested to facilitate and block, respectively, the Ca spikes, and polarization of layer I will be tested to block the antidromic action. The overall potential field, phi(x,y,z,t), and the conductivity tensor G(x,y,z) will be measured in order to calculate the net extracellular current field, J(x,y,z,t) and the pattern of transmembrane current flow in depth, im(z,t). This information is important in locating the affected cells in depth, z, and in interpreting the effects of the various agents. Convulsant agents will include strychnine, bicuculline, penicillin, cobalt and ferric ions. The r wave is of major interest, for it is found in rodents, rabbits, marsupial and prosimians but not in carnivores or simians. Anatomical, histochemical and electrophysiological techniques will be used to determine whether this component reflects an excitatory collateral action of pyramidal tract neurons, or some other phenomenon. To aid in attaining these objectives, a fully automated research laboratory is being re-implemented on a new computing system, the potential field and conductivity measurements will be made and analyzed with this computing system.